The Life of the Caterpillar,
by J. Henri Fabre, 1916

XIII: THE SENSE OF SMELL

IN PHYSICS we hear of nothing nowadays but the
Röntgen rays, which penetrate dense bodies
and photograph the invisible for US. A fine
discovery, but how insignificant in face of the
surprises which the future reserves for us when,
better-informed of the why and wherefore of
things, we supplement with art the feebleness of
our senses and succeed in rivalling, be it ever so
little, the keenness of perception revealed by the
brute creation.

How enviable, in many cases, is this animal
superiority! It teaches us the poverty of our
attainments; it declares the mediocrity of our
sensory apparatus; it gives us evidence of
impressions foreign to our nature; it proclaims
realities so far in excess of our attributes that
they astound us.

A wretched caterpillar, the Pine Processionary,
splits his back into meteorological air-holes
which snuff the coming weather and
foretell the squall; the bird of prey, with its
incomparably long sight, sees from high in the
clouds the Field-mouse squatting on the ground;
the blinded Bats guide their flight without injury
to themselves amid Spallanzani's
[note 1]
inextricable maze of threads; the Carrier-pigeon,
though moved a hundred leagues from home,
infallibly regains his cote across immensities
which he has never traversed unaided; within the
limits of her humbler flight, a Bee, the
Chalicodoma,
[note 2]
also spans the unknown,
accomplishes a long journey and returns to her
mass of cells.

The man who has never seen a Dog hunting for
truffles does not know one of the finest
achievements of the sense of smell. Absorbed in
its functions, the animal trots along, with its
nose to the wind, at a moderate pace. It stops,
questions the ground with its nostrils, scratches
for a few seconds, without undue excitement, and
looks up at its master:

"Here we are," it seems to say,
"here we
are! On ny word of honour as a Dog, there's a
truffle here."

And it speaks the truth. The master digs at the
point indicated. If the trowel goes astray, the
Dog shows the man how to put it right by sniffing
at the bottom of the hole. Do not be afraid of
the stones and roots in between: despite the depth
and intervening obstacles, the tuber will come. A
Dog's nose cannot lie.

"Subtlety of smell," you say.

I have no objection, if by that you mean that the
animal's nasal passages are the organ of
perception; but is the thing perceived always a
mere smell, in the ordinary acceptation of the
word, an effluvium such as our own senses
understand it? I have some reason to doubt this.
Let us set the matter forth.

I have had the good fortune on several occasions
to accompany a Dog who was a great expet at his
trade. Certainly he was nothing to look at, ths
artist whom I was so anxious to see at work: just
a Dog, placid and deliberate in his ways, ugly,
unkempt; the sort of Dog that you would never
admit to your fireside. Talent and poverty often
go hand in hand.

His master, a celebrated rabassier[note 3]
in the village, convinced that I had no intention
of stealing his secrets and one day setting up in
competition, allowed me to join him in his
expeditions, a favour which he did not often
grant. The worthy man was quite willing to fall
in with my views, once he saw that I was not an
apprentice but merely an enquirer who made
drawings
[note 4]
and wrote down lists of
underground vegetable things, instead of marketing
my bagful of treasure-trove, the glory of the
Christmas Turkey.

It was agreed between us that the Dog should act
as he pleased and receive a bit of bread as his
reward after each discovery, indiscriminately.
Every spot scratched up by his paws was to be dug
and the object indicated extracted without our
troubling about its commercial value. I no case
was the master's experience to intervene and
divert the dog from a spot where practice told him
that nothing saleable was to be found, for, in
drawing up my botanical lists, I preferred
wretched and unmarketable products to the choicest
morsels, though these of course were welcomed when
they appeared.

Thus conducted, the underground botanizing was
very fruitful. With his perspicacious nose, the
Dog made me gather indifferently the large and the
small, the fresh and the putrid, the scented and
the unscented, the fragrant and the stinking. I
was amazed at my collection, which comprised the
greater part of the hypogean fungi in my
neighbourhood.

What a variety of structure and above all of
odour, the primary quality in this question of
scent! There are some that have nothing more
noticeable than a vague fungous mustiness, which
is more or less evident in all. Some smell of
turnips, of rotten cabbage; some are fetid enough
to fill the collector's house with their stench.
The real truffle alone possesses the aroma dear to
the epicure.

If smell, as we understand it, is the Dog's only
guide, how does he manage to find his way through
all these incongruous odours?

Is he apprised of the contents of the soil by a
general emanation, the fungous effluvium common to
the different species? In that case an extremely
embarrassing question arises.

I paid some attention to the ordinary mushrooms,
many of which, as yet invisible, announced their
coming as imminent by cracking the surface of the
ground. Now I never saw the Dog stop at any of
those points where my eyes divined the cryptogam
pushing back the earth with the thrust of its cap,
points where the ordinary fungous smell was
certainly most pronounced. He passed them by
scornfully, with not a sniff, with not a stroke of
his paw. And yet the thing was underground; and
its reek was similar to others which he sometimes
pointed out to us.

I came back from the Dog's school with the
conviction that the truffle-detecting nose has a
better guide than smell, in the sense in which our
olfactory powers realize it. It must perceive, in
addition, effluvia of a different order, full of
mystery to us, who are not equipped accordingly.
Light has its dark rays, which are without effect
upon our retinæ, but not apparently upon
all. Why should not
the domain of smell have its secret emanations,
unknown to our senses but perceptible to a
differently constructed organ of smell?

If the scent of the Dog leaves us perplexed to
this extent, that it is impossible for us to say
exactly or even to suspect what it perceives, it
at least tells us plainly that we should be
greatly mistaken to compare every thing by human
standards. The world of sensations is far larger
than the limits of our sensibility admit. What a
number of facts in the working of the forces of
nature escape us for want of organs delicate
enough to perceive them!

The unknown, that inexhaustible field which the
future will cultivate, holds harvests in store for
us beside which our present knowledge is but a
pitiful gleaning. Under the sickle of science
sheaves will one day fall whose grain to-day would
seem a senseless paradox. Scientific illusions?
Not so, if you please, but undeniable and positive
realities, affirmed by the animal world, which in
certain respects has a great advantage over the
world of man.

In spite of his long professional practice, in
spite of the aroma of the tuber which he
is seeking, the rabassier cannot guess
the presence of the truffle, which ripens in
winter underground to a depth of eighteen inches
or so; he needs the aid of the Dog or the Pig,
whose scent pries into the secrets of the soil.
Well, these secrets are known to different insects
even better than to our two helpers. In order to
discover the tuber on which their family of grubs
is to be fed, they possess a scent of exceptional
perfection.

Long ago, from truffles dug up spoilt and teeming
with vermin and placed in this condition in a
glass jar with a layer of fresh sand, I obtained
first a small red Beetle (Anisotoma
cinnamomea,
PANZ.) and then various Diptera, including
a Sapromyzon, who, with her sluggish flight and
feeble frame, reminds me of a Fly, clad in yellow
velvet, known as Scatophaga scybalaria,
that placid frequenter of human excrement in
autumn.

The latter finds her truffle on the surface of the
ground, at the foot of a wall or hedge, man's
usual hasty refuge in the country; but how does
the other know at what point underground lies
hers, or rather her grubs' truffle? To go down
and hunt about in the depths is beyond her power.
Her frail
limbs, which the moving of a grain of sand would
warp; her wings, which, if extended, would block
her way through a gorge; her dress of stiff silk,
militating against a smooth passage: these are all
against her. The Sapromyzon is obliged to lay her
eggs on the surface of the soil, but she must do
so at the very spot beneath which the truffle
lies, for the tiny grubs would die if they had to
roam at random until they came upon their
provender, which is always sparsely distributed.

The truffle-hunting Fly is therefore informed by
her sense of smell of the spots favourable to her
maternal plans; she possesses the scent of the
rabassier Dog, indeed probably a better
one, for she knows things by nature, having never
been taught, whereas her rival has only received
an artificial education.

It would be interesting to follow the Sapromyzon's
manueuvres, but the idea strikes me as
impracticable. The insect is rare, flies away
quickly and is soon out of sight. To observe it
closely, to watch it at work would involve a great
loss of time and a degree of assiduity of which I
do not feel capable. Another discoverer of
underground fungi shall
reveal what the Fly could hardly be expected to
show us.

This is a pretty little black Beetle, with a pale
and velvety belly, round as a cherrystone and much
the same size. The insect's official title is
Bolboceras gallicus, MULS. By rubbing the tip
of its abdomen against the edge of its wing-cases
it emits a soft chirrup similar to that of the
little birds when their mother comes home with
their food. The male wears a graceful horn on his
head, copied on a smaller scale from that of the
Spanish Copris.
[note 5]

Deceived by this armour, I at first took the
insect for a member of the Dung-beetles'
corporation and brought it up as such in
captivity. I served it with these stercoral
dainties which are most appreciated by its
presumed colleagues. But never, no, never did it
consent to touch them. Fie, for shame Dung to a
Bolboceras! Well! What on earth did I take him
for? The epicure expects something very
different. He wants not exactly the truffle of
our banquets, but its equivalent.

This characteristic was not displayed to me
without patient investigation on my part. At
the southern foot of the Sérignan hills,
not far from the village, stands a thicket of
maritime pines, alternating with rows of
cypress-trees. Here, at the season of All
Saints, after the autumnal rains, the
mushrooms abound that frequent the
Coniferæ, in particular the delicious
milk-mushroom, which turns green at any part
that is bruised and sheds tears of blood when
you break it.
[note 6]
In the mild days of
autumn this is the favourite walk of my
household, being far enough to exercise young
legs and near enough not to tire them.

They find everything there: old Magpies' nests,
formed of bundles of twigs; Jays squabbling with
one another, after filling their crops with acorns
on the oaks hard by; Rabbits suddenly starting out
of a rosemary-bush, showing their little white
upturned scuts; Geotrupes
[note 7]
hoarding away
food for the winter and heaping up their rubbish
on the
sand, soft to the touch, easy to dig into tunnels,
easy to build into, rows of huts which we thatch
with moss and surmount with a bit of reed by way
of a chimney; and the delicious lunch off an apple
to the sound of the &Aelig;olian harps softly
sighing through the pine-needles!

Yes, for the children it is a real paradise, where
one goes as a reward for well-learnt lessons. The
grown-ups also have their share of enjoyment. As
far as I am concerned, I have for many years been
watching two insects here, without succeeding in
discovering their family secrets. One of them is
Minotaurus typhæus,
[note 8]
whose
male carries on his corselet three spikes pointing
in front of him. The old writers used to call him
the Phalangist, because of his armour, which may
be compared with the three lines of spears of the
Macedonian phalanx.

He is a robust fellow, who cares nothing for the
winter. All through the cold season, whenever the
weather turns a trifle milder, he leaves his house
discreetly, at nightfall, and gathers, in the
immediate neighbourhood
of his burrow, a few Sheep-droppings, ancient,
olive-shaped remains dried by the summer sun. He
heaps them in a stack at the bottom of his larder,
shuts the door and eats. When the provisions are
all crumbed and drained of their niggardly juices,
he climbs back to the surface and renews his
stores. Thus does he spend the winter, never
resting from his work, except when the weather is
too severe.

The second object of my observations in the
pine-wood is the Bolboceras. His burrows,
distributed here and there, among those of the
Minotaur, are easily distinguished. The
Phalangist's are surmounted by a bulky mound the
materials of which are heaped into a cylinder as
long as one's finger. Each of these rolls is a
load of rubbish pushed outside by the digger,
thrusting with his back from below. The orifice
moreover is closed whenever the Beetle is at home,
either enlarging the shaft or peacefully enjoying
his possessions.

The Bolboceras' lodging is open and surrounded
merely by a padding of sand. Its depth is slight,
nine inches, hardly more. It goes straight down
in very loose soil. It is easily inspected,
therefore, if we take care first
to dig a trench in front of it, which will enable
us later to cut away the perpendicular wall, slice
by slice, with the blade of a knife. The burrow
then appears at full length, from top to bottom,
in a semicylindrical shape.

Often the violated dwelling-house is empty. The
insect has left during the night, having finished
its business there and gone to settle elsewhere.
The Bolboceras is a nomad, a night-walker, who
leaves his home without regret and easily acquires
a new one. Sometimes also the insect is found at
the bottom of the pit: at one time a male, at
another a female, but never the two at a time.
The sexes, both equally zealous in digging
burrows, work separately, not together. This is
not, in fact, a family residence, containing the
nursery of the young; it is a temporary abode, dug
by each occupant for his own comfort.

Sometimes we find nothing there but the
well-sinker, surprised during his work of
excavation; sometimes, lastly--and the case is not
uncommon--the hermit of the crypt embraces with
his legs a small hypogean fungus, either intact or
partly consumed. He clutches it convulsively,
refuses to be parted from it. It is his booty,
his fortune, his
worldly goods. Scattered crumbs tell us that we
have caught him feasting.

Let us take his prize away from him. We shall see
a sort of irregular, rugged purse, closed on every
side and varying in size between a pea and a
cherry. Outside it is reddish, rough with little
warts; inside it is smooth and white. The spores,
which are ovoid and diaphanous, are contained, in
rows of eight, in long satchels. By these
characteristics we recognize an underground
cryptogamous product, nearly related to the
truffles and known to botanists as Hydnocystis
arenaria,TUL.

This throws a light upon the habits of the
Bolboceras and upon the reason why his burrows are
so frequently renewed. In the calm of the
twilight, the little gadabout takes to the fields,
chirruping softly as he goes, cheering himself
with song. He explores the soil, questions it as
to its contents, just as the Dog does when hunting
for truffles. His sense of smell warns him when
the coveted morsel is underneath, covered by a few
inches of sand. Certain of the exact spot where
the thing lies, he digs straight down and never
fails to reach it. As long as the provisions
last, he
does not go out again. Blissfully he feeds at the
bottom of the well, heedless of the door left open
or hardly barred.

When no more food remains, he moves, looking for
another loaf, which will become the excuse for a
fresh burrow, to be abandoned in its turn. Each
fungus consumed represents a new house, which is a
mere refectory, a traveller's refreshment-room.
Thus are the autumn and spring, the seasons of the
hydnocystis, spent in the pleasures of the table,
from one home to the next.

To study the rabassier insect more
closely, in my own house, I should need a little
store of its favourite fare. It would be waste of
time to seek for it myself, by digging at random:
the little cryptogam is not so plentiful that I
can hope to strike it with my trowel without a
guide. The truffle-hunter needs his Dog; my
informer shall be the Bolboceras himself. Behold
me turned into a rabassier of a new kind.
I reveal my secret, which can only raise a smile
from my original instructor in underground botany,
if he should ever hear of my singular form of
competition.

The subterranean fungi occur only at certain
points, often in groups. Now the Beetle
has been this way; with his delicate scent he has
recognized the site as good, for the burrows are
numerous hereabouts. We will therefore dig near
the holes. The clue is accurate. In a few hours,
thanks to the tracks left by the Bolboceras, I
possess a handful of hydnocystes. It s the first
time that I have gathered this particular fungus.
Let us now catch the insect That presents no
difficulties: we have only to dig up the burrows.

I make my experiments the same evening, filling a
large earthen pan with fresh, sifted sand. With a
stick as thick as my finger, I make six vertical
tunnels in the sand, two decimetres
[note 9]
deep
and placed at a suitable distance apart. A
hydnocystis is lowered to the bottom of each; and
I insert a fine straw, to show me the exact
position later. Lastly, I fill up the six
cavities with caked sand. When this surface has
been carefully smoothed, so that the level is
everywhere the same, except for the six straws,
landmarks that mean nothing to the Bolboceras, I
let loose my captives, covering them with a
wire-gauze cage. There are eight of them.

At first there is nothing to see save the
inevitable uneasiness due to the incidents of
their exhumation, transport and confinement in an
unknown place. My exiles from home try to escape,
climb up the wire, burrow right at the edge of the
enclosure. Night falls and things grow calmer.
Two hours later, I come to take a last look at
them. Three are still buried under a thin layer
of sand. The five others have each dug a
perpendicular shaft at the very foot of the straws
which tell me where the fungi lie. Next morning,
the sixth straw has its well like the others.

This is the moment to see what is happening
underground. I remove the sand methodically in
vertical slices. At the bottom of each burrow is
a Bolboceras eating his truffle, the hydnocystis.

Let us repeat the experiment with the
partly-consumed victuals. The result is the same.
At one brief, nocturnal spell of work, the dainty
is discovered underground and reached by means of
a gallery which runs plumb to the spot where the
morsel lies. There is no hesitation, no trial
excavation guided by guesswork. This is proved by
the surface of the soil, which everywhere is just
as I left it when I smoothed it down. The
insect could not have made straighter for the
coveted object had it been guided by sight; it
always digs at the foot of the straws, my
sign-posts. The Dog, nosing the ground for
truffles, hardly achieves this degree of
precision.

Has the hydnocystis then a very pungent smell,
able to give such positive information to its
consumer's scent? Not at all. To our nostrils it
is a neutral object, devoid of any appreciable
olfactory character. A tiny pebble taken out of
the ground would impress us just as much with its
faint aroma of fresh earth. As a revealer of
underground fungous products, the Bolboceras here
rivals the Dog. He would even rise superior to
the Dog, were he able to generalize. But he is a
rigorous specialist: he knows only the
hydnocystis. Nothing else, so far as I am aware,
tempts him to dig.
[note 10]

Both of them search the subsoil very closely, at
the level of the ground; and the object which they
seek is not far down. Were they farther away,
neither the Dog nor the
insect would notice effluvia so subtle, not even
the smell of a truffle. To make an impression at
a great distance, powerful odours are needed,
capable of perception by our olfactory sense.
Then the exploiters of the odorous thing come
hastening up on all sides from afar.

When, for the purpose of my studies, I require
insects that dissect corpses, I expose a dead Mole
in the sun, in a distant corner of the enclosure.
As soon as the animal swells, distended by the
gases of putrefaction, and the skin begins to turn
green and the fur to fall from it, up come numbers
of Silphæ
[note 11]
and Dermestes,
[note 12]
[note]
Necrophori
[note 13]
[note]
and other Burying-beetles, of
whom one would find not a single specimen in the
garden, or even in the neighbourhood, without this
bait.

They have been informed by their sense of smell,
at a great distance all around, whereas I myself
can avoid the stench by taking a few steps back.
Compared with their scent, mine is contemptible;
but still, in their
case as well as mine, there is really here what
our language calls a smell.

I can do better still with the flower of the
dragon arum (Arum dracunculus), so
remarkable for its shape and for its unequalled
stench. Imagine a wide, lanceolate blade, of a
clarety purple, half a yard long and rolled below
into an ovoid pouch the size of a hen's egg.
Through the opening of this wallet rises a central
column springing from the bottom, a long,
bright-green club, encircled at its base by two
bracelets, one of ovaries, the other of stamens.
Such, briefly described, is the flower, or rather
the inflorescence, of the dragon arum.

For two days it exhales a frightful stench of
carrion, worse than the proximity of a dead Dog
would yield. During the hottest part of the day,
with a wind blowing, it is loathsome, unbearable.
Let us brave the infected atmosphere and go up to
it; we shall behold a curious sight.

Informed by the foul odour, which spreads far and
wide, various insects come flying along, such
insects as make sausage-meat of small
corpses--Toads, Adders, Lizards, Hedgehogs,
Moles, Field-mice--which the
husbandman hits with his spade and flings away
disembowelled on the foot-path. They swoop down
upon the great leaf, which, with its livid purple,
looks like a strip of meat gone bad; they caper
about, intoxicated by the smell of corpse which
they love; they roll down the slope and are
swallowed up in the purse. After a few hours of
bright sunshine, the receptacle is full.

Let us look inside, through the narrow opening.
No elsewhere could you see such a crowd. It is a
mad whirl of backs and bellies, of wing-cases and
legs, swarming, rolling over and over, amid the
snap of interlocked joints, rising and falling,
floating and sinking, seething and bubbling
without end. It is a drunken revel, an epidemic
of delirium tremens.

Some, few as yet, emerging from the mass, climb to
the opening by means of the central pole or the
walls of the enclosure. Will they take wing and
make their escape? Not they! Standing on the
brink of the chasm, almost free, they drop back
into the whirlpool, in a fresh bout of
intoxication. The bait is irresistible. Not one
of
them will quit the assembly until the evening, or
perhaps next morning, when the heady fumes have
evaporated. Then the mass becomes disentangled;
and the insects extricate themselves from one
another's embraces and slowly, as it were
regretfully, leave the place and fly away. At the
bottom of this devil's purse remains a heap of
dead and dying, of severed limbs and disjointed
wing-cases, the inevitable result of the frenzied
orgy. Soon, Wood-lice, Earwigs and Ants will
arrive and devour the deceased.

What were they doing there? Were they the
prisoners of the flower? Had it converted itself
into a trap which allowed them to enter, but
prevented them from escaping, by means of a fence
of converging hairs? No, they were not prisoners;
they had full liberty to go away, as is shown by
the final exodus, which is effected without
impediment. Deceived by a false odour, were they
doing their best to instal their eggs, as they
would have done under a corpse? Not that either.
There is no trace of an attempt at egg-laying in
the dragon's purse. They came, enticed by the
smell of a dead body, their supreme delight; they
were drunk with corpse;
and they spun round frantically in an undertakers'
carnival.

When the bacchanal dance is at its height, I try
to count the number of the arrivals. I rip up the
floral pouch and pour its contents into a flask.
Absolutely tipsy though they be, many would escape
during the census, which I wish to take
accurately. A few drops of carbon bisulphide
deprive the crowd of motion. The counting then
shows that there were over four hundred. Such was
the living billow which I saw surging just now in
the dragon's purse.

Another detail deserves attention just as much as
this enormous figure; and that is the complete
absence of a number of other genera which are as
passionately fond of small corpses as are the
Dermestes and Saprini. My charnel-houses of Moles
never fail to be visited by the Silphæ and
Necrophori: Silpha sinuata,FABR.; S.
rugosa,
LIN.; S. obscura, LIN.; Necrophorus
vestigator,
HERSCH. The reek of the dragon arum leaves
them all indifferent. None of them is represented
in the ten flowers which I examine.

Nor are any Diptera, those other devotees of
corruption. Several Flies, some grey or bluey,
others a metallic green, come up, it is true,
settle on the edge of the flower and even find
their way into the fetid wallet; but they are
almost immediately undeceived and fly away. Only
the Dermestes and Saprini stay behind. Why?

My friend Bull, as decent a Dog as ever lived, had
this among many other eccentricities: if he found
in the dust of the road the dried up corpse of a
Mole flattened under the heels of the passers-by,
mummified by the heat of the sun, he would revel
in rolling himself over it from the tip of his
nose to the end
of his tail; he would rub himself in it over and
over again, shaken with nervous spasms, turning
first on one side, then on the other. It was his
sachet of musk, his flask of eau-de-Cologne. When
scented to his liking, he would get up, shake
himself and trot off, pleased as Punch with his
pomade. Let us not abuse him and, above all, let
us not discuss the matter. There are tastes of
all kinds in this world.

Why should not some of the insects that dote on
the smell of the dead have similar habits?
Dermestes and Saprini come to the dragon arum; all
day long they swarm in throngs, although free to
go away; many of them die in the riot of the orgy.
It is no rich provender that keeps them, for the
flower gives them nothing to eat; it is not a
question of laying eggs, for they take good care
not to settle their grubs in that famine-stricken
spot. What are they doing here, the frenzied
ones? Apparently intoxicating themselves with
fetidness, just as Bull did on the carcass of a
mole.

And this intoxication of smell attracts them from
every part around, from very far perhaps, one
cannot tell. Even so the
Necrophori, in quest of an establishment for their
young, hasten from the fields to my putrefying
Moles. Both are informed by a potent smell, which
offends our nostrils sixty yards away, but which
travels ahead and delights them at distances where
our own power of scent ceases.

The hydnocystis, the Bolboceras' treat, has none
of these violent emanations, capable of being
diffused through space; it is devoid of smell, at
least to us. The insect that hunts for it does
not come from a distance; it inhabits the very
places where the cryptogam lies. However faint
the effluvia of the underground morsel, the prying
epicure, equipped for the purpose, has every
facility for perceiving them: he operates close
by, on the surface of the soil. The Dog's case is
the same: he goes along searching, with his nose
to the ground. Then, too, the real truffle, the
essential object of his quest, possesses a most
pronounced odour.

But what are we to say of the Great Peacock and
the Banded Monk, making their way to the female
born in captivity? They hasten from the ends of
the horizon. What do they perceive at that
distance? Is it really
an odour, as our physiology understands the word?
I cannot bring myself to believe it.

The Dog smells the truffle by sniffing the earth,
quite close to the tuber; he finds his master at
great distances by consulting the scent of his
footprints. But is he able to discover the
truffle hundreds of yards away, miles away? Can
he join his master in the complete absence of a
trail? Certainly not. For all his fineness of
scent, the Dog is incapable of such a feat, which
is performed, however by the Moth, who is put off
neither by distance nor by the lack of any traces
out of doors of the female hatched on my table.

It is a recognized fact that smell, ordinary
smell, the smell that affects our nostrils,
consists of molecules emanating from the scented
body. The odorous matter dissolves and is
diffused throughout the air by communicating to
the air its aroma, even as sugar dissolves and is
diffused in water by communicating to the water
its sweetness. Smell and taste touch each other
at some points; in both cases there is a contact
between the material particles that give the
impression and the sensitive papillæ that
receive it.

Nothing can be simpler or clearer than that
the
dragon arum elaborates an intensely strong essence
with which the air is impregnated and infected all
around. Thus the Dermestes and Saprini, those
passionate lovers of carrion smells, are informed
by molecular diffusion. In the same way, the
putrid Toad gives out and disseminates the
stinking atoms that are the Necrophorus' delight.

But what is materially emitted by the female
Bombyx or Great Peacock? Nothing, according to
our sense of smell. And this nothing is supposed,
when the males congregate, to saturate an immense
circle, several miles in radius, with its
molecules! What the horrible stench of the dragon
arum is unable to do the absence of odour is
believed to accomplish! However divisible matter
may be, the mind refuses to accept such
conclusions. It would be tantamount to reddening
a lake with an atom of carmine, to filling
immensity with nothing.

Another argument. When my study is saturated
beforehand with pungent odours which ought to
overcome and destroy the most delicate effluvia,
the male Moths arrive without the least sign of
embarrassment.

A loud noise kills the faint note and
prevents it from being heard; a bright light
eclipses a feeble gleam.. These are waves of the
same nature. But the roar of thunder cannot cause
the least jet of light to pale; nor can the
dazzling glory of the sun stifle the least sound.
Being of different natures, light and sound do not
influence each other.

The experiment with the lavender-oil,
naphthaline and the rest would therefore seem to
prove that odour proceeds from two sources. For
emission substitute undulation; and the problem of
the Great Peacock is explained. Without losing
any of its substance, a luminous point shakes the
ether with its vibrations and fills a circle of
indefinite width with light. This must almost
express the working of the mother Bombyx'
tell-tale discharge. It does not emit molecules:
it vibrates; it sets in motion waves capable of
spreading to distances incompatible with a real
diffusion of matter.

In its entirety, smell would thus seem to have two
domains: that of the particles dissolved in the
air and that of the ethereal waves. The first
alone is known to us. It belongs also to the
insect. It is this which informs the Saprinus of
the dragon arum's
fetidity and the Silpha and Necrophorus of the
stench of the Mole.

The second, which is far superior in its range
through space, escapes us altogether, because we
lack the necessary sensory equipment. The Great
Peacock and the Banded Monk know it at the time of
the nuptial rejoicings. And many others must
share it in various degrees, according to the
exigencies of their mode of life.

Like light, odour has its X-rays. Should science
one day, instructed by the insect, endow us with a
radiograph of smells, this artificial nose will
open out to us a world of marvels.

______

[note 1]:
The Abbé Lazaro Spallanzani
(1729-99), an early experimenter in natural
history and author of a number of important works
on the circulation of the blood, on digestion, on
generation and on microscopic animals. Cf.
The Hunting Wasps: chap.
xix.--Translator's Note.